Kirk Wallace wrote:
> As far as the "up to speed" signal - for
> tapping, the active axis is electronically geared to the spindle, so no
> matter what the spindle is doing the axis will try to follow it. I am
> thinking that the "up to speed" signal might be used for fault sensing
> for spindles without encoders, but I don't think any work has been done
> on EMC in this regard.
>
On the Mazak the spindle drive's "at speed" output was routed into the
PC and is used for a couple of things.
1) During gear changes it tells the ladder logic that the drive has
reached the commanded speed and it is safe to shift. You don't
want to shift at 4000 RPM, but you also need to avoid shifting at
zero speed - slow movement helps the gear teeth line up. We set
the Mazak up to shift at 15 RPM.
2) We connected the at-speed through a HAL inverter to feedhold, so that
if you code a spindle start followed by a cutting move, it won't put
the tool into the material until the spindle has ramped up. We did
that after having a close call at the CNC workshop in 2006 - the
the spindle turned on, rapided over to the part, and started cutting
while it was only going about half speed. As I watched it happen I
had visions of dragging the 3/8" cutter through steel while it was
barely turning. Snap!
Regards,
John Kasunich
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